If an individual was to be brought here illegally at say an early age, they could potentially find themselves ineligible to enter this country legally. If, out of desperation, an individual came across looking for work or refuge, was found and deported, but found a way to attempt to return via legal means why not permit the endeavor? Have they not learned the consequences of the illegal action and sought correct means to the situation?
Should we also ban stupid kids who shoplift from ever getting jobs because they did something stupid once? No, give them their due punishment, but when they want to do things right, let them.